Alpha-Amylases (alpha-1,4-glucan-4-glucanohydrolases, EC 3.2.1.1) constitute a group of enzymes which catalyze hydrolysis of starch and other linear and branched 1,4-glucosidic oligo- and polysaccharides.
There is a very extensive body of patent and scientific literature relating to this industrially very important class of enzymes.
A number of alpha-amylase such as Termamyl-like alpha-amylases variants are known from, e.g., WO 90/11352, WO 95/10603, WO 95/26397, WO 96/23873, WO 96/23874 and WO 97/41213.
Among recent disclosure relating to alpha-amylases, WO 96/23874 provides three-dimensional, X-ray crystal structural data for a Termamyl-like alpha-amylase, referred to as BA2, which consists of the 300 N-terminal amino acid residues of the B. amyloliquefaciens alpha-amylase comprising the amino acid sequence shown in SEQ ID NO: 6 and amino acids 301-483 of the C-terminal end of the B. licheniformis alpha-amylase comprising the amino acid sequence shown in SEQ ID NO: 4 (the latter is available commercially under the tradename Termamyl™), and which is thus closely related to the industrially important Bacillus alpha-amylases (which in the present context are embraced within the meaning of the term “Termamyl-like alpha-amylases”, and which include, inter alia, the B. licheniformis, B. amyloliquefaciens and B. stearothermophilus alpha-amylases). WO 96/23874 further describes methodology for designing, on the basis of an analysis of the structure of a parent Termamyl-like alpha-amylase, variants of the parent Termamyl-like alpha-amylase which exhibit altered properties relative to the parent.
WO 96/23874 and WO 97/41213 (Novo Nordisk) disclose Termamyl-like alpha-amylase variants with an altered cleavage pattern containing mutations in the amino acid residues V54, D53, Y56, Q333, G57 and A52 of the sequence shown in SEQ ID NO: 4.